[Scripts] make convert_arm_sdot_to_machine_code.py be compatible with python2 test=develop

lite/tools/convert_arm_sdot_to_machine_code.py

@@ -12,6 +12,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+from __future__ import print_function
+
 import argparse
 import sys
 import os